Hollow beams



July l0, 1956 B. BRUNTON 2,753,601

HOLLOW BEAMS Filed Sept. 6, 1952 1 2,753,601 HOLLOW BEAMS Bernard Brunton, London, England. Application September 6, 1952, Serial No. 308,237 @aims priority, application Great Britain June 30, 1952 2 Claims. (Cl. 20m-.5)

The present invention relates to hollow beams more particularly to hollow beams of the type in which a self supporting framework is enclosed by an outer skin of sheet material rigidly secured thereto, and has as an object to provide an improved construction of such beams.

The invention is especially applicable to the construction of wooden hollow beams in which a framework of wooden battens is encased in a skin of plywood rigidly secured thereto. In the known constructions of such wooden beams it has been found that although in order to give the required strength to the beam, the plywood skin should have a good tensile strength, this in itself has the disadvantage that the plywood stretches under load resulting in a corresponding deformation of the beam. This disadvantage is substantially overcome in a beam according to the invention by providing a Construction in which a pair of trusses constructed of wooden battens are secured in parallel spaced apart relation and are surrounded by a plywood skin to form a hollow beam, the plywood on the outer faces of the trusses being rigidly secured to the top and bottom members of the trusses. ln this way, stretching of the plywood skin under strain is substantially avoided since the said top and bottom members are rigidly connected by the struts and brace` members of the truss.

The invention will now be described with reference to the accompanying drawing illustrating one embodiment thereof and in which:

Figure 1 is a side elevation of a hollow wooden beam constructed according to the invention;

Figure 2 is a. similar view of a portion of the beam drawn to an enlarged scale partly in section and with parts broken away to show more clearly details of construction; and

Figure 3 is a section taken along the line III-III of Figure 2 drawn to a still larger scale.

In the drawing the beam indicated generally at 1 is formed of a pair of trusses indicated generally at 2 and 3 secured together in spaced parallel relation by top and bottom plywood panels 4 and 5 and faced on their outer sides by plywood skins 6 and 7 respectively. The skins 6 and 7 have secured thereto on the outer face a triangular fillet 8, a plurality of spaced top battens 9 and a bottom batten 10. These attachments serve for the location and support of members extending between adjacent beams and are not concerned with the present invention. Similarly, upright blocks 11 which serve to locate the ends of the beam on suitable supporting columns are also secured to the outer surfaces of the skins 6 and 7.

The truss 2 is formed of an upper member 12 and a lower member 13 connected together at spaced intervals by vertical struts 14 and inclined brace members 15. The corresponding members of the truss 3 are indicated respectively at 12a, 13a, 14a and 15a. The joints between the struts and brace members and the upper and lower members respectively are reinforced by plates of plywood i6 and 16a to which the said members are secure. The plates are gripped between the upper or lower member, as the case may be, and a further upper member 17 or lower member 18 as will be clearly seen in Figure 3, the plates and members being securely fastened together by gluing and nailing.

Additional upper members 19 and 19a, and additional lower members 20 and 20a are provided respectively in the trusses 2 and 3. The said additional members extend nited lStates Patent O over only a portion of the length of the beam as will be seen in Figure 2, and afford additional strength where required. The size and length of the members 19 and 20 will depend on the span of the beam and the load to be carried thereby.

As will be seen from Figure 3 of the drawing, the upper panel ft is secured to the members 12 and 17 of truss 2 and members 12a and 17a of girder 3 by glueing and nailing while the lower panel 5 is similarly secured to members 13, 1S, 13a and 18a of the said trusses. The trusses are thus held rigidly in spaced relation by the pancls 4 and 5 but in order to further strengthen the beam, an apex block 21 extends between and is secured to the trusses 2 and 3.

The plywood skins 6 and 7 are respectively secured to the trusses 2 and 3 by glueing and nailing to the upper members 12 and i9 and the lower members 13 and 2b of the truss 2 and to the corresponding members 12a, 19a, 13a and 20a of the truss 3.

The above described construction provides a hollow beam which is eminently suitable for use in prefabricated building structures and which combines lightness and Strength and at the same time is substantially free from the aforementioned diiculty due to stretching of the plywood skin.

What I claim is:

1. A fabricated hollow structure building element comprising a pair of self-supporting truss structures extending lengthwise of the element, and a casing secured to and enclosing the said structures and securing the structures in spaced apart relation transversely of vthe element, the sides of the truss structures facing outwardly and inwardly of the structural element respectively each of the said truss structures including an upper and a lower longitudinally extending member, and the said casing comprising top and bottom sheet members abutting and secured to the said upper and lower members of each truss structure respectively for securing the truss structures in said transversely spaced apart relation, and side sheet members abutting and secured to the outwardly facing side of each of the truss structures.

2. A fabricated hollow wooden beam comprising a pair of self supporting trusses extending the length of the beam, and an outer casing secured to and enclosing the said trusses and securing the trusses in transverse spaced apart relation, the sides of the trusses facing outwardly and inwardly respectively of the beam, each of the said trusses comprising an upper and a lower longitudinally extending member secured together in vertically spaced apart relation by vertical struts and inclined brace members, the said outer casing comprising a top sheet member overlying and secured to the upper surface of said upper member of each truss, a bottom sheet member underlying and secured to the under surface of the said lower member of each truss, the said top and bottom sheet members securing the trusses in the said transverse spaced relation, and side sheet members overlying and securd to the outwardly facing side of the upper and lower m-embers of each truss respectively.

References Cited in the tile of this patent UNITED STATES PATENTS 1,899,924 Breda Mar. 7, 1933 2,002,506 Loudenback May 28, 1935 2,150,754 Williams c- Mar. 14, 1939 2,347,879 Brunton et al. May 2, 1944 FOREIGN PATENTS 905,625 France Dec. l0, 1945 OTHER REFERENCES Architectural Forum, Sept. 1947, pages 117 and 118. 

